AN AIR COOLING SYSTEM

Abstract: To obtain a cooling system of compact design and with redundancy and free cold, heat exchangers in a cooling system are combined such that by said cooling system the inside air is cooled by means of cold liquid or boiling cooling medium in a combined evaporator-air cooler (2) and the outside air cools warm liquid or condensing cooling medium in a combined condensor-liquid cooler (1). Free cold may be utilized when the difference in temperature between inside air and outside air is big enough and the outside air is sufficiently cold. Liquid cooled by the outside air in the combined condenser-liquid cooler (1) and then heated by the warm inside air in the combined evaporator-air cooler (2) will then take care of the entire heat load alone. In other cases, the compressor system can provide the cooling. The free-cooling system can serve as a redundant system for the compressor system when the latter is out of order.

Description: AN AIR-COOLING SYSTEM TECHNICAL FIELD The present invention relates to a cooling system for cooling air, such as indoor air, wherein the cooled air can be used for cooling telecommunications equipment for instance, and wherein the air is used to carry away thermal energy. DESCRIPTION OF THE BACKGROUND ART Various thermal energy dissipating systems are known to the art in which air is used as a heat transporting medium. A feature which is common to one group of systems is that air is treated, i.e. cooled, and then recirculated in the room to be cooled or in the room in which a particular item is to be cooled. Thus, a room in which telecommunications equipment is installed can be cooled in several different ways. For instance, the indoor air, or room air, can be cooled with the aid of a compressor cooling system or with the aid of a cold liquid. A common feature of both these methods is that the heat exchangers used to effect heat transfer between coolant and air and between liquid and air respectively have similar constructions. Free cold is used in order to keep operating costs as low as possible. By free cold is meant essentially that when outdoor temperatures are low, the air is used directly in this state for cooling purposes, instead of operating an energy-demand- ing cooling system, such as a compressor cooling system, for instance. The use of free cold can save considerable quanti¬ ties of energy. In one method of cooling with cold air, liquid is circulated and cooled by the cold outdoor air and then used to cool the room air. This method is efficient up to a given outdoor temperature, whereafter the air must be cooled with the aid of some other means, for instance with the aid of a compressor cooling system. A free-cold cooling system could well be used as a backup system for a compressor cooling system and brought into use should the compressor cooling system malfunction for some reason. In cases such as these, the free cooling system is referred to as a redundancy for the compressor cooling system. SUMMARY OF THE INVENTION With the intention of obtaining a cooling system of compact design which can be embodied in one single unit with redun¬ dancy and free cold, the heat exchangers of the cooling system have been combined so that the room air is cooled in the cooling system by means of cold liquid or by means of a boiling coolant in a combined evaporator-air cooler, and the outdoor air cools warm liquid or condensing coolant in a combined condenser-liquid cooler. Free cold may be utilized when the difference in temperature between indoor air, or room air, and outdoor air is sufficiently large and the outdoor air is sufficiently cold. Liquid that is cooled by the outside air in the combined condenser-liquid cooler (EC) and then heated by the room air in the combined evaporator air-cooler ( CC) is then capable of handling the entire heat load alone. In other instances, the air can be cooled with the aid of the compressor cooling system. The free-cold cooling system shall also be capable of functioning as a redundancy for the compressor system should said system fail. For instance, in the event of a power cut the system fans and liquid pump may be operated on batteries, via a rectifier or some like device. At the end of the power cut, the compressor cooling system can be restarted and the batteries recharged. It is also feasible to run both systems simultaneously under certain circumstances, so as to obtain an increased cooling effect. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 illustrates a cooling system for cooling indoor air in accordance with the invention. Fig. 2 illustrates an inventive cooling-controlling and monitoring system. BEST MODE OF CARRYING OUT THE INVENTION Fig. 1 illustrates schematically the main components of a cooling system, which may be incorporated in a single unit, for example in telecommunications equipment, having a combined condenser-liquid cooler 1 (EC) and a combined evaporator-air cooler 2 (CC). The Figure also shows how these components are mutually connected. The combined condenser- liquid cooler 1 is either placed outdoors, as indicated at 10, or is installed in an external wall 9, and the combined evaporator-air cooler 2 is installed indoors, as indicated at 11, and functions as a heat exchanger in coaction with each of two separate pipe systems, of which one pipe system 8 conveys liquid and the other pipe system 7 conveys a coolant. As indicated, there may be provided between the outdoor space 10 and the indoor space 11 a partition wall 9 in which the cooling system can be placed in the form of a unit. Seen in the direction of flow, the coolant circuit 7 includes a compressor 5 downstream of the evaporator air cooler 2 and an expansion valve 12 downstream of the condens¬ er-liquid cooler 1. The liquid circuit 8 includes a liquid pump 6. A condenser fan 3 is connected to the combined condenser-liquid cooler l. An evaporator fan 4 is connected to the combined evaporator-air cooler 2. The compressor cooling system is said to constitute the main cooling system of the aforesaid room air cooling system, and hence it can be said in summary that the present invention provides a system for obtaining free cold at outdoor tempera- tures which enables this and a redundancy function which can be used in the event of a failure in the main cooling system. The evaporator and condenser of the main cooling system thus include an extra liquid piping system which is arranged in parallel with the main system and which is intended for use in low outdoor temperatures, as before mentioned, and which will function to cool the air inside an apparatus room, for instance, should the main system fail. The two parallel systems may utilize common heat exchanging surfaces for heat exchange with the air. Because the same evaporator fan and the same condenser fan are used in all operational instances, it is possible to save considerable space and costs in comparison with other free-cooling and redundancy systems, and the combined system can be constructed as one single compact unit. Figure 2 is a greatly simplified illustration of a cooling- system controlling and monitoring system. The outdoor temperature and indoor temperature are registered with the aid of temperature sensors 13 and 14, and optionally also the level of temperature in the combined condenser-liquid cooler 1 and the combined evaporator-air cooler 2 respectively. The illustrated system also includes a control unit 15 which receives measurement signals from the various parts of the system and also from the temperature sensors. These measure¬ ment signals are processed and stored in the control unit and may, for instance, be compared with reference values, such as set-point values, which are either calculated or stored, and delivers control signals to the various parts of the system for optimal operation of the cooling system. Measure¬ ment signals and/or control signals are indicated by broken lines in the Figure. In the event of a power cut, running of the cooling system can be kept running with the aid of the battery function of the control unit subsequent to making adjustments to the system through the medium of control signals.

Claims: AMENDED CLAIMS [received by the International Bureau on 22 May 1995 (22.05.95); original claim 1 amended ; remaining claims unchanged (1 page )] 1. A cooling air system, such as an indoor air cooling system, characterized in that the cooling system includes two parallel cooling circuits (7, 8) which share common heat exchangers (1, 2) and of which one circuit (7) is intended to conduct coolant and includes an evaporator (2) , a compres¬ sor (5) , a condenser (1) and an expansion valve (12) and the other circuit (8) is intended to conduct a heat absorbing medium and includes two coolers (1, 2) and a pump (6) ; in that one (1) of said heat exchangers is located outdoors and is comprised of a combined condenser and cooler for the coolant and the heat absorbing medium respectively, heat being emitted to the ambient air; and in that the other (2) of said heat exchangers is located indoors and is comprised of a combined evaporator and cooler for the coolant and heat absorbing medium circulating in said circuits, wherein the coolant and heat absorbing medium extract heat from the ambient air. 2. A cooling system according to Claim l, characterized in that the system includes fans (3, 4) for coaction with the heat exchangers (l, 2) . 3. A cooling system according to Claim 1, characterized by a control unit (15) for monitoring and controlling the cooling system with regard to measurement signals obtained from different parts of the system and from temperature sensors (13, 14) .

Inventors: FORSMAN BERTIL, FORSMAN, BERTIL
Applicants: ERICSSON TELEFON AB L M, FORSMAN BERTIL, FORSMAN, BERTIL, TELEFONAKTIEBOLAGET L M ERICSSON
Application year: 1994
Main classification: F25D16
IPC codes: F24F1, F25B25, F25D1, F25D16, H05K7